The dynamics of cytosolic Ca2+ concentration exhibits oscillations with a wide range of periods. It was suggested
in recent years by several modelling studies that these oscillations do not result from an oscillatory local dynamics
but that fluctuations drive the formation of spatial and temporal structures in a non-oscillatory dynamic regime.
Fluctuations arise from the random opening and closing of release channels on the membrane of the endoplasmic
reticulum. Consequently, the interspike interval (ISI) has not a sharp value as with regular oscillations but
distributions of ISI arise. We present these distributions and relate them to underlying processes. Oscillations
with long average ISI can be comprehended as repetitive wave triggering. The standard deviation of the ISI
approximates the inverse of the triggering rate. Oscillations with short average ISI are often complex oscillations
consisting of base line oscillations and intermittent oscillations on an elevated cytosolic Ca2+ level.